Linear and torsional mechanical characteristics of intact and reconstructed scapholunate ligaments.

The mechanical behavior of human scapholunate ligaments is not well understood. Presently, intact scapholunate specimens were mechanically tested in linear distraction and torsion. Fresh bovine tendon grafts were used to reconstruct the scapholunate interval and the tests repeated. Tests yielded the following average values for intact specimens: linear stiffness (48.9 N/mm), linear load retained at 100 s (44%), torsional stiffness (19.5 N mm/deg), torque remaining at 100 seconds (66%), torque-to-failure (1253.9 N mm), and angle-to-failure (50.4 deg). Tests showed the following average values for reconstructed specimens: linear stiffness (5.4 N/mm), linear load retained at 100 s (49%), torsional stiffness (12.6 N mm/deg), torque remaining at 100 s (71%), torque-to-failure (936.8 N mm), and angle-to-failure (54.5 deg). There were no statistically significant differences between the intact and reconstructed specimens, with the exception of linear stiffness. Biomechanically, this is the first study in the literature to quantify torsional stress relaxation, failure torque, and failure angle for the intact and repaired human scapholunate ligament. Surgically, reconstruction with bovine tendon may warrant further investigation as a method to potentially retain function and strength after scapholunate injury.